April 14, 2017 — For the first time, scientists have recorded a spring fish migration by conducting DNA tests on water samples.

The work was a collaboration of Rockefeller University and the Urban Coast Institute at Monmouth University.

According to the study’s report, environmental DNA called eDNA, collected from one-liter samples drawn weekly from New York’s East and Hudson rivers over six months last year, revealed the presence or absence of several key fish species passing through the water on each test day.

The bits of DNA recovered found the presence of menhaden, herring species, black sea bass, striped bass, tautog (blackfish), mummichog, bay anchovy, bluefish, oyster toadfish, Atlantic silverside, and conger eel. In total it found the presence of 42 species.

Using eDNA is a way to monitor fish migrations that involves a fraction of the effort and cost of trawling, all without harming the fish, the study said.

It also said it can be used to estimate the abundance and distribution of diverse fish species and other forms of marine life in the dark waters of rivers, lakes, and seas.